


Little Baby Rin And Her Big Sister

by Gothdresser



Category: Fate/hollow ataraxia, Fate/stay night (Visual Novel), Fate/stay night - All Media Types
Genre: Diaper, F/F, Little Miss Rincontinent, Pee, Scat, Soiling, Wetting, diapermessing, dirty diaper, messing, peeing, pooping, urinating
Language: English
Status: Completed
Published: 2020-06-01
Updated: 2020-06-01
Packaged: 2021-03-03 03:01:50
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,500
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24487894
Author URL: https://archiveofourown.org/users/Gothdresser/pseuds/Gothdresser
Summary: Despite being an older sister already, Rin Tohsaka finds herself in a stinky situation as the Einzbern heir puts the younger girl in her place. Illya is a year older than her after all, even if almost a foot shorter.This thought was based on some pictures of Illya teasing and babying Rin, and they were just so good for the role reversal.
Relationships: Illyasviel von Einzbern/Tohsaka Rin, Tohsaka Rin/Illyasviel von Einzbern
Kudos: 19





	Little Baby Rin And Her Big Sister

“Okay, go on and play, Rin, I’ll be back in a second. I just have to call Sella quickly, but make sure to come to me if you have to go potty~” Letting go of the bigger girl’s hand, the short silver-haired loli headed over to a nearby bench and set a bag down. Crinkling rustled next to her while Illya took out her phone and dialed up her maid as she turned her attention away from the oddly-dressed younger girl.

Nervously rubbing her thighs together was the perfect student of Homurahara Academy, Rin Tohsaka herself, although somewhat unusually dressed, both in general and technically for her age. A red turtleneck and a black skirt were her typical garb, and yet she still wore something similar to that, only a little more… childish. Rin’s dress was a red bodice with a black skirt, a thick white stripe around the waist to accent the cuteness, but to call it a short dress was an understatement.

On any other girl, the dress would barely cover her panties, if at all, but that would be if Rin was actually wearing panties. Instead, with the front already a little discolored, a thick diaper adorned her waist as she softly crinkled more into the park. To think this all originated from just a couple of nights of bedwetting and some accidents at Illya’s castle. Still, it wasn’t her fault that such a place was so massive! Even her own estate paled in comparison to how much wealth the Einzberns had, which almost made her feel better about not having to pay for her own diapers.

The fact that she was in diapers, for the most part, was still upsetting, but after about a month or so of this treatment, she had almost surprisingly gotten used to it. It wasn’t all too bad since she didn’t have to deal with cleaning herself up, and not having to worry about money was relieving, even if she had to end up relieving herself in her underwear in most cases. Even a couple of complacent accidents in her panties had happened in the meantime, and Rin ended up sometimes preferring dirty diapers rather than a butt as red as her usual clothes.

Speaking of dirty diapers, the brunette looked around the park, not only to see if others were around that might recognize her but also for a small place to hide. Being in a diaper pretty much meant she was likely going to have to use it, which she had already done a little. If Illya teasing her for tinkling in her diaper was embarrassing enough, then the pressure at her rear might be worse since the little girl really loved to see herself as the older sister. That was likely why Illya pushed herself into such a role since she knew the girl was without parents or siblings for a long time. Still, there was the shame in already being an older sister and suddenly becoming the little sister while getting changed by a smaller but older girl. 

Being almost a foot taller than her ‘big’ sister didn’t mean much though, as Rin wandered under the play structure, putting a spinning tic-tac-toe panel between herself and Illya. All that height quickly disappeared when she squatted down, a light blush appearing on her face while she tried to give relief to her big padded butt. Pooping in public was sometimes still tough for her when it wasn’t more of an accident, although Rin had started to unconsciously give herself a trigger to make it easier.

Without realizing it, one of her thumbs hovered by her lips, slipping between them while Rin began to softly groan. Pushing had finally come to fruition as something big and thick and mushy slipped out of her large ass, a soft crinkling coming from her diaper as it began to fill up. While her messes were already of a decent size, they only became bigger when she held off on using her personal potty for a period of time. That was still a lesson for her to learn to make it easier to consider her underwear a toilet while out and about, but that would only come with time and practice.

As for now, her potty time was coming to an end, and Rin’s shoulders relaxed, not yet realizing her thumb was in her mouth until the spinning of the tic-tac-toe panels surprised her. Stumbling back as she did, the messy girl’s dirty diaper hit the tanbark below her, squishing as she groaned out again. Not only for the icky feeling of that smell spreading all around her butt and smushing between her asscheeks, but also knowing it’d only make her change worse. “Eeeeh?! W-who’s there?” She should’ve been alone to use her diaper, but someone had to have been watching her, especially since her super short dress did nothing to hide the big bulge drooping down her diaper.

“Awww, I’m gone for a few minutes, and little Rin is already a pottypants? And you even said you didn’t have to go potty before we left.” Out from behind came a familiar purple-and-white dress, a finger by Illya’s smug smile as she watched the younger girl soil her diaper. Then again, that was her usual though, with her loving to see how embarrassed Rin could be, more so when going potty in her pants. Said diaper would have to be changed soon enough though but that’s why Illya had a bag slung over her shoulder, something white and crinkly clearly peaking out 

Even with Rin returning to full height, Illya not having a big mess packed in her underwear easily made her the more mature one between the two of them, her dominance continuing as she walked behind Rin and hooked a finger to open the back of her waistband. “My my, you really had to go, didn’t you? And you even sat on it too, making my job so tough... But is that all you had to do, or do you still have to go potty?” With one hand squishing the back of Rin’s bulging diaper, Illya’s other hand felt itself rubbing the front.

Rin couldn’t help but grumble a little as all that messing did trigger another need of hers, antsy on her feet as she could feel the small hand pressing against her padded crotch. Oh well, she was in a diaper for a reason, one that she not only messed but had already wet a little as well. Opening the floodgates, the big baby girl did enjoy that feeling of peeing in her diaper, hissing coming from the inside of her diaper as she let it all out. “Th-there, I’m done going potty.”

Mentioning having finished wasn’t even quite needed since the sudden warmth of the diaper against her hand told Illya all that she needed to know. However, she still loved how adorable Rin could be with her phrasing with the big girl admitting to using her diaper so much. “That’s a good girl. Hopefully, you feel better now that you’re finished using the toilet.” A well-used toilet at that with how much she watched Rin’s diaper sag down, unable to keep a smile off of her face at seeing how her little sister was more like a baby sister. “Do you think your diaper can hold anything else, or would you like a change after squishing on your big mushy tush?” She could be teasing and capable of punishments, but Illya didn’t like to be too cruel with Rin, giving her a chance for a change since she did give her a surprise.

“I guess I could do with one, but it’s not like I wanted you to change me. It’s just smart to have one since I already sat on my dirty diaper, and in case I need to go again.” She was hesitant to admit it out loud, but Rin could really feel how full her diaper was. The initial wetting wasn’t too bad, although the combination of filling up both sides really made it droop right now. It was about mid-thigh level already, and even just shifting in place made her crinkle and squish around.

And if she wasn’t blushing hard enough already, Rin could feel the shame of having her diaper on display as she was led out from under the play structure. She just had to hope no one else would come to the playground anytime soon, pulling down the front of her dress despite not covering a thing, and certainly not the back with the huge poopy that sagged down her diaper.

Tugging the embarrassed pamperpacker along, Illya had her hand around Rin’s wrist while bringing her towards the bathroom, and not the one around Rin’s waist. “Come on, stinky pants. Maybe you can play with some of the little kids that come here around this time when we’re done, but let’s get you changed into a nice clean diapee first~”


End file.
